ATMEGA164P-20AU Atmel, ATMEGA164P-20AU Datasheet - Page 150

• Manufacturer Part Number: ATMEGA164P-20AU
• Description: IC MCU AVR 16K FLASH 44-TQFP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA164P-20AU

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 20MHz
• Connectivity: I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 32
• Program Memory Size: 16KB (8K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 512 x 8
• Ram Size: 1K x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 44-TQFP, 44-VQFP
• Package: 44TQFP
• Device Core: AVR
• Family Name: ATmega
• Maximum Speed: 20 MHz
• Operating Supply Voltage: 3.3|5 V
• Data Bus Width: 8 Bit
• Number Of Programmable I/os: 32
• Interface Type: JTAG/TWI/SPI/USART
• On-chip Adc: 8-chx10-bit
• Number Of Timers: 3
• Processor Series: ATMEGA16x
• Core: AVR8
• Data Ram Size: 1 KB
• Maximum Clock Frequency: 20 MHz
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• 3rd Party Development Tools: EWAVR, EWAVR-BL
• Development Tools By Supplier: ATAVRDRAGON, ATSTK500, ATSTK600, ATAVRISP2, ATAVRONEKIT
• Minimum Operating Temperature: - 40 C
• For Use With: ATSTK600-TQFP44 - STK600 SOCKET/ADAPTER 44-TQFPATSTK600 - DEV KIT FOR AVR/AVR32770-1007 - ISP 4PORT ATMEL AVR MCU SPI/JTAG770-1005 - ISP 4PORT FOR ATMEL AVR MCU JTAG770-1004 - ISP 4PORT FOR ATMEL AVR MCU SPIATAVRISP2 - PROGRAMMER AVR IN SYSTEM
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

14.9
8011O–AVR–07/10
Asynchronous Operation of Timer/Counter2
Figure 14-11 on page 150
Figure 14-11. Timer/Counter Timing Diagram, Clear Timer on Compare Match mode, with Pres-
When Timer/Counter2 operates asynchronously, some considerations must be taken.
• Warning: When switching between asynchronous and synchronous clocking of
• The CPU main clock frequency must be more than four times the Oscillator frequency.
• When writing to one of the registers TCNT2, OCR2x, or TCCR2x, the value is transferred to a
• When entering Power-save or ADC Noise Reduction mode after having written to TCNT2,
Timer/Counter2, the Timer Registers TCNT2, OCR2x, and TCCR2x might be corrupted. A safe
procedure for switching clock source is:
temporary register, and latched after two positive edges on TOSC1. The user should not write
a new value before the contents of the temporary register have been transferred to its
destination. Each of the five mentioned registers have their individual temporary register, which
means that, for example, writing to TCNT2 does not disturb an OCR2x write in progress. To
detect that a transfer to the destination register has taken place, the Asynchronous Status
Register – ASSR has been implemented.
OCR2x, or TCCR2x, the user must wait until the written register has been updated if
Timer/Counter2 is used to wake up the device. Otherwise, the MCU will enter sleep mode
before the changes are effective. This is particularly important if any of the Output Compare2
interrupt is used to wake up the device, since the Output Compare function is disabled during
writing to OCR2x or TCNT2. If the write cycle is not finished, and the MCU enters sleep mode
a. Disable the Timer/Counter2 interrupts by clearing OCIE2x and TOIE2.
b. Select clock source by setting AS2 as appropriate.
c. Write new values to TCNT2, OCR2x, and TCCR2x.
d. To switch to asynchronous operation: Wait for TCN2UB, OCR2xUB, and TCR2xUB.
e. Clear the Timer/Counter2 Interrupt Flags.
f.
TCNTn
(clk
(CTC)
OCRnx
OCFnx
clk
clk
Enable interrupts, if needed.
I/O
I/O
Tn
/8)
caler (f
clk_I/O
TOP - 1
shows the setting of OCF2A and the clearing of TCNT2 in CTC mode.
/8)
TOP
TOP
ATmega164P/324P/644P
BOTTOM
BOTTOM + 1
150